The invention concerns a crane or excavator for traversing a load hanging from a support cable that has a computer-controlled regulation system to damp the swinging of the load.
In particular, the invention addresses the load swing damping in the case of cranes or excavators, which permits movement of a load hanging from a cable in at least three degrees of freedom. Such cranes or excavators have a rotating mechanism that can be mounted on a chassis that serves to rotate the crane or excavator. Furthermore, there is a luffing mechanism for raising or lowering a boom. Finally, the crane or excavator includes a lifting mechanism to lift or lower the load hanging from the cable. Such cranes or excavators are in use in the most widely varied designs. For example, mobile port cranes, ships' cranes, offshore cranes, caterpillar-mounted cranes and stripping shovels can be named.
When traversing a load hanging from a cable using such a crane or excavator, swings arise that, on the one hand, can be attributed to the movement of the crane or excavator itself, and also to outside interference such as, for example, wind. Already in the past, efforts have been undertaken to suppress swinging oscillations in the case of load cranes.
Thus, DE 127 80 79 describes an arrangement for the automatic suppression of the swinging of a load hanging by means of a cable from a cable attachment point, which is movable in the horizontal plane, in the case of movement of the cable attachment point in at least one horizontal coordinate, in which the speed of the cable attachment point is affected in the horizontal plane by a regulating circuit dependent upon a value derived from the angle of deflection of the load cable against the end position.
DE 20 22 745 shows an arrangement to suppress the swinging of a load that is attached by means of a cable on the trolley carriage of a crane, whose drive is equipped with a rotational speed device and a distance regulating device with a regulating arrangement that accelerates the trolley carriage, taking into account the period of oscillation during a first part of the distance traveled by the carriage, and which decelerates it during the last part of this distance in such a manner that the movement of the carriage and the oscillation of the load at the destination are both equal to zero.
From DE 321 04 50, there became known a device on lifting equipment for the automatic control of the movement of the load carrier with damping of the swing of the load hanging from it arising during acceleration or braking of the load during an acceleration or braking time interval. The basic idea is based on the simple mathematical pendulum. The trolley and load mass is not included for the calculation of the movement. Coulomb friction and friction proportional to speed of the trolley or rolling car are not taken into account.
In order to be able to transport a load as rapidly as possible from its point of origin to its point of destination, DE 322 83 02 suggests controlling the rotational speed of the drive motor of the trolley by means of a computer, so that the trolley and the load carrier are moved during the steady state run at the same speed and that the damping of swinging is accomplished in the shortest possible time. The computer known from DE 322 83 02 works on a computer program for the solution of the differential equations that apply to the undamped two-mass oscillation system made up of the trolley and the load, where the coulomb and speed-proportional friction of the trolley or rolling crane drive are not taken into account.
In the procedure that became known from DE 37 10 492, the speeds between the destinations along the way are selected in such a manner that, after traveling half the total distance between the starting point and the destination, the swinging deflection is always equal to zero.
The procedure for damping load swinging that became known from DE 39 33 527 includes a normal speed-position regulation.
DE 691 19 913 covers a process to control the setting of a swinging load in which the deviation between the theoretical and actual position of the load is formed in a first regulating circuit. This is derived multiplied by a correction factor and added to the theoretical position of the movable carrier. In a second regulating circuit, the theoretical position of the movable carrier is compared to the actual version, multiplied by a constant and added to the theoretical speed of the movable carrier.
DE 44 02 563 discusses a procedure for the regulating of electrical drives for lifting gear with a load hanging from a cable, which, due to the dynamics of description equations, generates the desired progression of the speed of the crane trolley and feeds it to a speed and current regulation. Furthermore, the computer device can be expanded by a position regulator for the load.
Regulating processes that became known from DE 127 80 79, DE 393 35 27 and DE 691 19 913 require a cable angle sensor for load swing damping. In the expanded design according to DE 44 02 563, this sensor is also required. Since this cable and/or sensor results in substantial costs, it is advantageous if the load swings can be compensated for even without the sensor.
The process of DE 44 02 563 in its basic version also requires at least the crane trolley speed. In DE 20 22 745 as well, multiple sensors are required for load swing damping.
Thus, in DE 20 22 745, at least a rotational speed and position measurement of the crane trolley must be performed.
DE 37 10 492, as well, needs at least the trolley or rolling crane position as supplementary sensors.
Alternatively to this procedure, another application, which became know, for example, from DE 32 10 450 and DE 322 83 02, suggests solving the differential equations on which the system is based and, based on this, determining a control strategy for the system in order to suppress load swings where, in the case of DE 32 10 450, the cable length, and in the case of DE 322 83 02, the cable length and the load mass, are measured. However, in these systems, the friction effects from adhesive friction and friction proportional to velocity, which are not negligible, are not taken into account. Even DE 44 02 563 does not take into account friction and damping times.